We could also point out that he's both a dude and double her bodyweight, but there's another factor I think the artist is aiming at:

There's a certain enzyme in the stomach (which probably has a fancy greek/latin name I would struggle to pronounce) which breaks down alcohol faster. About 90% of caucasian folks have this enzyme, though "lightweights" and "cheap drunks" who were born without it exist. This 90% defines our ideas about what is a "normal" amount of booze to drink.

However in Japan those ratios are reversed. 90% are born without the enzyme, and they define what is considered a "normal" amount of booze to drink in their culture.

All other factors affecting drunkenness like sex, mass, and adaptation apply too, of course, but it's like multiplying a large or small base number; the end result is exponentially different.

Still, a warning before you go challenging any Japanese bars to drink them all under the table, remember they have that 10% born with the enzyme too. Pick a drinking fight, and they will call forward their local "Heavyweight" drinker, who not only has the enzyme, but a LOT of practice under his belt from contests like this.